CVE-2026-6736: CWE-306 Missing Authentication for Critical Function in GitHub Enterprise Server
CVE-2026-6736 is an authentication bypass vulnerability in GitHub Enterprise Server versions prior to 3.21. It allows an unauthenticated attacker to create a local user account despite external identity provider enforcement. The vulnerability occurs because the signup endpoint does not properly enforce authentication restrictions when external authentication is enabled. The attacker can establish a session with default base permissions on the instance. Exploitation requires network access to a vulnerable GitHub Enterprise Server instance configured with an external authentication provider. The issue was fixed in versions 3.20.2, 3.19.
AI Analysis
Technical Summary
An authentication bypass vulnerability (CWE-306) in GitHub Enterprise Server allows unauthenticated attackers to create local user accounts by exploiting improper enforcement of authentication restrictions on the signup endpoint when external authentication is enabled. This bypasses the configured external identity provider, enabling account creation and session establishment without identity provider validation. The created accounts have default base permissions. The vulnerability affects all versions prior to 3.21 and requires network access to the affected instance. Fixed in multiple patch releases starting with 3.16.18 through 3.20.2.
Potential Impact
An attacker with network access to a vulnerable GitHub Enterprise Server instance can create local user accounts without authenticating through the external identity provider. The attacker gains an account with default base permissions, which could allow limited unauthorized access to the server's resources. This bypass undermines the external authentication controls configured on the instance.
Mitigation Recommendations
This vulnerability is fixed in GitHub Enterprise Server versions 3.20.2, 3.19.6, 3.18.9, 3.17.15, and 3.16.18. Users should upgrade to one of these fixed versions or later to remediate the issue. Since this is not a cloud service, patching the affected server instances is required. Patch status is confirmed by the vendor advisory information embedded in the description.
CVE-2026-6736: CWE-306 Missing Authentication for Critical Function in GitHub Enterprise Server
Description
CVE-2026-6736 is an authentication bypass vulnerability in GitHub Enterprise Server versions prior to 3.21. It allows an unauthenticated attacker to create a local user account despite external identity provider enforcement. The vulnerability occurs because the signup endpoint does not properly enforce authentication restrictions when external authentication is enabled. The attacker can establish a session with default base permissions on the instance. Exploitation requires network access to a vulnerable GitHub Enterprise Server instance configured with an external authentication provider. The issue was fixed in versions 3.20.2, 3.19.
CVSS v4.0
Score 6.3medium
Affected software
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
An authentication bypass vulnerability (CWE-306) in GitHub Enterprise Server allows unauthenticated attackers to create local user accounts by exploiting improper enforcement of authentication restrictions on the signup endpoint when external authentication is enabled. This bypasses the configured external identity provider, enabling account creation and session establishment without identity provider validation. The created accounts have default base permissions. The vulnerability affects all versions prior to 3.21 and requires network access to the affected instance. Fixed in multiple patch releases starting with 3.16.18 through 3.20.2.
Potential Impact
An attacker with network access to a vulnerable GitHub Enterprise Server instance can create local user accounts without authenticating through the external identity provider. The attacker gains an account with default base permissions, which could allow limited unauthorized access to the server's resources. This bypass undermines the external authentication controls configured on the instance.
Mitigation Recommendations
This vulnerability is fixed in GitHub Enterprise Server versions 3.20.2, 3.19.6, 3.18.9, 3.17.15, and 3.16.18. Users should upgrade to one of these fixed versions or later to remediate the issue. Since this is not a cloud service, patching the affected server instances is required. Patch status is confirmed by the vendor advisory information embedded in the description.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_P
- Date Reserved
- 2026-04-21T02:53:28.704Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69fd029ecbff5d861038a136
Added to database: 05/07/2026, 21:22:38 UTC
Last enriched: 05/15/2026, 11:00:30 UTC
Last updated: 07/31/2026, 19:23:00 UTC
Views: 115
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.